I have a song I listen to here on the computer sometimes. I listened to it many times, yet yesterday was the first time I listened to it in the car. It sounded way different, there was a lower melody that I couldn't even hear on the computer. It was so weirdly different. I've also listened to it with headphones and it didn't sound like that. But I plugged my phone into a stereo and played it, and it sounded like it did in the car.

I'm guessing the computer speakers and my headphones don't have much low range ability.

I try and avoid listening to music on a computer. Even with the best speakers/headphones, some of the frequency response gets missed. There is still a lot to be said for traditional vinyl, and even CD's.

By the way, if you want really good headphones that you can wear for long periods without them feeling uncomfortable, these take a lot of beating, they're not standard in most radio stations for nothing 

Most of what I listen to comes from the computer, however, I send it to an Apple Airplay device connected to a Yamaha receiver in the living room. The sound is comparable to a CD. If I listen to vinyl or a cassette, then I have no choice because my only in-use tape deck and turntable are connected to the Yamaha receiver and they sound quite good, too.

Computer speakers are only good for "preview" when you want to quickly identify a piece of music, for instance. Car speakers are hit-and-miss, I find. Depends also on ambient noise (tires, rain, wind, engine rumble, etc) although most are better than computer speakers.

I try and avoid listening to music on a computer. Even with the best speakers/headphones, some of the frequency response gets missed.

Wrong. This is entirely dependent on the DAC. While DACs can vary slightly, all modern DACs easily reproduce the entire audible frequency.

If you cannot hear the low frequencies, your amplification and/or transducers are to blame. If by "even with the best speakers" you mean "even with the best 'computer' speakers"... well, 'computer' speakers are generally trash, yes. The easiest fix is to get a subwoofer. The best option is to pipe the audio out to an external amplifier with speakers.

There are many factors that will limit the frequency response.

1- Your own ears. When you get older, your response to hight frequencies decreases.

2- Your speakers of couse.

3- Your audio file. Will not be the same a full bitrate PCM file to a 128kbps MP3, or the 96kbps ACC from Youtube.

4- Your DAC, the cheapests DACs lacks the response to high frequencies.

5- Your headpone cord. You cord have a paracitic R-C low pass filter.

A car is the worst place to listen to music. Car manufacturers spend millions to develop music systems that sound good to the typical car buyer. But they have to deal with the weird acoustics of a car interior and the noises that are made when driving on various roads.

Speakers are all over the map on sound quality. Where speakers are placed (and make sure their polarity is correct) will determine the low-end response of them.

Your best bet for "honest" sound is to acquire a GOOD pair of headphones and use good source material played through decent audio equipment. Don't need "expensive" audiophile stuff, a good home stereo or a PC/laptop with decent hardware will suffice. Remember some sound sources are better than others, some CD's aren't recorded very well or some sound files aren't compressed or processed correctly.
Personally, I use Audio-Technica ATH-M50x headphones. They are fairly "flat" response and generally held in high regard for their price range. If you search enough, you'll even find some cheap headphones that sound good too, but you need to do lots of research. I have heard of some very good $20 headphones.

In my home, we have Bose speakers, Pioneer speakers, Sony speakers, the ATH-M50x headphones, Technics TT, Pioneer CD changer, JVC cassette player, Pioneer receiver, etc. mostly from the 70's-90's. We listen to vinyl, cassette, CD and even stream through a retired smartphone connected into the AUX. It all sounds good because the hardware is good stuff.

A car is the worst place to listen to music.

If you've got a V8 engine behind you, like in the Ferrari Dino GT4, then who the **** needs music..?  

There is by far not any limitation in the electronic part (DAC, amplifiers,...; even the cheapest ones are never the part affecting the sound quality). The time when the exact DAC type matters is long gone...

The limitations are mainly computer speakers (with so limited box volume it is miracle they sound like they do). To prevent speaker overload and so distortion or damage, the software cuts out the low part of the spectrum the speakers are not able to radiate anyway. Plus sometimes the intention to make a lot of noise with just the 2x1.5W available with all mobile devices (3.6 V battery with 4 Ohm BTL connected speakers just can not give any more power), the most common trick is to concentrate all the power just to the midrange and cut out the rest.
Again, pure SW trickery (VLC player did so to such extend it burned the speakers in I think HP notebooks, where the speakers were designed to be exposed to the full power only at low frequencies, where the deep cone and coil displacement ensured good air cooling of the coil; when this power came only at midrange, the movement so cooling effect was not present and so the coil overheated, HP denying to cover that by warranty arguing the VLC was not preinstalled)

Also hearing protection software limiters (limit the total peak pressure, as well as displacement when earphonrs are detected). These limiters usually start to cut out the low part of the audio, where is most of the energy and keep the rest, so it still appear loud.

In both cases the limitations are done in a way to not add any audible distortion and to sound like the low part never was there, so if you have no compare, it appears to you as normal.

I would expect similar trickery to be used with all the miniature wireless headphones, this time with an intention to save the tiny battery power by reducing the required output power...

If you connect it to an external audio system, these limiters are switched off and so the sound output goes straight as it was recorded, with the spectrum complete.

Wait... Sorry to interrupt but shouldn't this be in off topic?

Wait... Sorry to interrupt but shouldn't this be in off topic?

Yeah, I just noticed it. Could moderator move it please, to correct forum?

Yeah, I just noticed it. Could moderator move it please, to correct forum?

You can move it manually to off-topic in the tools of your thread.

From the first day I got a computer with a soundcard...I've always had my computer connected directly to my stereo receiver.

As teen i have built my own audio using speakers from old TVs and TDA2003 and similar single chip amplifiers, or occasionally using components desoldered from the same TVs... Nowadays i use big headphones